Preparation of organosilicon halides



Patented Au g. 7, 1945 2,380,995 PREPARATION OF ORGANOSILICON HALIDESEugene G. Rochow, Schenectady, N. Y., asslgnor to General ElectricCompany, a corporation of New York No Drawing. Application September 26,941,

. sci-n1 No. 412,459

17 Claims.

This invention relates to the preparation of organosilicon halides andmore particularly to the production 01 hydrocarbon-substituted siliconhalides.

The present invention is based on my discovery that organosiliconhalides, more particularly bydrocarbon-substituted silicon halides, canbe produced by eflecting reaction between silicon and a hydrocarbonhalide. The reaction may be carried out in the presence or absence of ametallic catalyst for the reaction. The silicon may be used as such orin the form 01' alloys or mixtures with metals, specifically metals thatthemselves are catalysts for the reaction between silicon and ahydrocarbon halide.

(Oi. ace-e07) It was known prior to my invention that hydrocarlionhalides could-be caused to react with elements other than silicon. Forexample, the

reaction of hydrocarbon halides with magnesium reactions are liquidphase reactions.

The reaction-oi hydrogen chloride with silicon also was known. Thus,'Combes ECompt, rend,

122, 531 (1896)] obtained a mixture of approximately 80% trichlorosilane(silicochloroform) and silicon tetrachloride by passing hydrogenchloride through an iron tube filled with silicon heated to 300 to 440C.

It also was known prior to my invention that varioushydrocarbon-substituted, silicon halides could be produced. The knownmethods of preparing such substituted silicon halides generally haveinvolved the use of the well-known Grignard reagent. Such a method 01'preparing methyl silicon chloride is described, for example, in mycopending application-Serial No. 287,787, filed August 1, 1939, nowPatent No. 2,258,218, issued October 7, 1941. The present inventionprovides an improved process for producing hydrocarbon-substitutedsilicon halides at lower unit reagent. 1

Briefly described, my invention resides in the improved method ofpreparing organosilicon halides, more particularlyhydrocarbon-substituted silicon halides,e.' g., alkyl silicon chlorides,bromides, etc., aryl silicon chlorides, bromides, etc.,

cost than is possible by the use of the Grignard which comprisesefiecting reaction between sili- 5 con and a hydrocarbon halide, e.- 8.,an alkyl chloride, bromide, eta, an aryl chloride, bromide, etc. In apreferred embodiment o! the invention, reaction is effected between thesilicon and the hydrocarbon halide while the latter is in vapor state,and, more particularly, while the said components are intimatelyassociated with a metallic catalyst (e. g., copper) for the reaction.For instance, the silicon may be in the form 01' an alloy thereof withcopper or other metal that has a catalytic effect upon the reactionbetween a silicon and a hydrocarbon halide.

One specific method feature'of' my invention is the new and improvedmethod of preparing, for example, methyl silicon chlorides whichcomprises bringing methyl chloride, more particularly gaseous methylchloride, into contact with a solid mass containing silicon, e. g., amass of silicon intimately associated with copper,- heating the saidmethyl chloride and silicon-containing mass at a temperaturesufllciently high to eflect reaction between the methyl chloride and thesilicon oi the said mass, and recovering the methyl silicon chlorides.

Another specific method feature 01' the invention is the method whichcomprises causing gaseous methyl chloride or other hydrocarbon halide ingaseousor vapor state to react with silicon intimately associated, as byalloying. with copper or other metallic catalyst for the reaction, saidreaction being carried'out' within the temperature range of 200 to 500C. or more, and recovering the hydrocarbon-substituted silicon halides.For example, the emuent gaseous reaction products may be cooled bysuitable means to obtain-a condensate comprising hydrocarbon-substitutedsilicon halides, specifically methyl silicon chlorides.

It was quite surprising and unexpected to find that anorganosiliconhalide, more particularly a hydrocarbon-substituted silicon halide,could be produced by eflecting reaction between silicon and ahydrocarbon halide, especially in view of the fact that silicon iscommonly considered to be a metalloid and shows little or no resemblanceto zinc, sodium, magnesium and the other highly electropositive metalsheretofore known to 'react with hydrocarbon halides.

In orderthat those skilled in the art better may understand how thepresent invention may be carried into effect, the following illustrativeexamples thereof are given. All percentages are by Weight.

' Example 1' A stream of gaseous methyl chloride w? passed into a heatedtube where it contacted silicon powdered to pa s through a 325-meshscreen. Areaction temperature of the order of 300 C. wasmaintainedwithin the tube. The products passing from the exit end of the reactiontube were condensed and the individual compounds subsequently separatedby fractional distillation. A typical condensate contains the followingcompounds in approximately the stated precentages:

1 Per cent Methyl silicon trichloride 52 Dimethyl silicon dichloride14.5 Silicochloroform- -10 Methyl dichlorosilane ,2-3 Silicontetramethyl Trace Trimethyl silicon chloride Trace Example 2 A reactiontube was charged with lumps of sintered silicon obtained by firingsilicon of approximately 325-mesh fineness in a hydrogenatmosphere at1300 C. Chlorobenzene vapor was passed through the tube. A reactiontemperature of apptoximately.600 C. was maintained within the tube. Thereaction products were condensed, yielding'a condensate comprisingphenyl silicon chlorides.

.' Example 3 A reaction vessel lined with copper and provided withinternal copper rollers was charged with 500 cc. chlorobenzene and 200grams of comminuted ,(minus mesh) copper-silicon alchanged bromobenzenefrom the phenyl silicon- Example 6 Bromobenzene was-allowed to (1119into a vertical tube filled with lumps of commercial copper-siliconalloy formed of approximately 50% each of copper and silicon. The tubewas heated to 400 C. in a combustion furnace and the bromobenzenetherefore was in vapor state during the reaction with the silicon of thecoppersilicon alloy. The products were condensed. The condensate wasdistilled to separate the unbromides produced by the reaction.

Example 7 A glass tube was packed with porous pills or pellets pressedfrom a mixture of copper and silicon powders. The pellets contained 80%siliconand20% copperandhadbeenfiredina hydrogen atmosphere at about 1050C. for two hours. (These contact masses and their preparation are morefully described and claimed in the copending application of Winton I.Patnode,

Serial No. 412,461, filed concurrently herewith and assigned to the sameas the present invention.) The tube was heated in a combustion furnacewhile a slow stream of methyl bromide was passed through it. Atapproximately 275 C. reaction occurred between the methyl by containingapproximately 50% each of silicon and copper. A reaction temperature ofthe order of 230 to 280 C. was maintained within the closed vessel for48 to '12 hours. During the reaction period the vessel was rotated, sothat the rollers performed a grinding action on the alloy. The reactionproducts comprised phenyl silicon trichloride, diphenyl and a tarrymaterial.

Example 4 Example 5 I A stream of gaseous methyl chloride was passedinto a heated tube-where it contacted silicon in the form of an alloy ofapproximately 50% each of silicon and copper. A reaction temperature ofthe order of 360 C. was maintained within the 'tube. The productspassing from the'exit end of the reaction tube were condensed.

The products may be condensed at temperatures of the order of, forexample-0 to 20 C.,

in which case any unreacted methyl chloride escapes; or, they may becondensed in a trap diphenyl silicon dichloride.

maintained at a temperature of, for instance,-

minus 80' C., in which case any unreacted methyl chloride condensesalong with the reaction products. The condensate comprised a mixture ofmethyl silicon chlorides (methyl chloroililanes). The individualcomponents of the condensate can be isolated, if'desired, by knownmethods, for instance by fractional distillation.

bromide and the silicon. A yellow liquid was readily condensed from theunreacted methyl bromide. From this liquid, methyl tribromosilane(boiling point 133.5 C.) and dimethyl dibromosilane (boiling point 112.3C.) were isolated by fractional distillation.

Example 8 Ethyl chloride was allowed to evaporate into a tube filledwith porous pellets prepared from a mixture of powdered silicon and 10%powdered copper as described under Example 7. The reaction temperaturewas maintained at 300 to 325 C. The reaction products condensed in theform of a yellow, fuming liquid which, upon fractional distillation, wasfound to contain approximately 27% ethyl silicon trichloride, 26%diethyl silicon dichloride and 37% silicon tetrachloride.

Example 9 A glass tube was packed with porous coppersilicon pellets suchas are described under Example 'l. The tube, inclined slightly downward,was heated to 280' to 300 C. while ethyl bromide was allowed to dripinto it. The products from the tube were condensed, yielding a yellowliquid comprising ethyl silicon bromides.

Example 10 Methyl iodide was allowed to drip into a sloping reactiontube charged with porous pellets formed from a mixture of 90% siliconand 10% copper and fired in hydrogen as described under Example 7. Thetube was heated within the temperature range of about 300' to 310' C.

Fifty-seven (57) grams of methyl iodide were passed'into the heated tubeover a period of two hours. A dark red liquid issued from thecondenserafiixedtothereactiontube. Thisllquid was distilled atatmospheric pressure. 'Besidea.

unreacted methyl. iodide, there was obtained a high-boiling yellowliquid comprising methyl silicon iodides.

Example 11 Gaseous methyl fluoride was passsdinto a tube aseopes filledwith porous pellets formed of 90% silicon and 10% copper and fired inhydrogen as described under Example 7. The reaction tube was heated ata. temperature of the order of 370 C. The products passing from the exitend of the tube were condensed. The condensate comprised unreactedmethyl fluoride and methyl silicon fluorides.

Example 12 Same as Example with the exception that a reactiontemperature of the order of.325 C. was maintained within the reactiontube.

Example 13 Same as Example 5 with the exception that the temperature ofthe reaction was of the order of 380 C. and the silicon was employed inthe form of a mixture of 95% comminuted silicon and 5% comminutedcopper.

It will be understood, of course, by those skilled in the art that myinvention is not limited to the specific hydrocarbon halides named inthe above illustrative examples and that any other hydrocarbon halidemay be employed as a reactant with the silicon, the conditions ofreaction generally being varied depending upon the particular startinghydrocarbon halide and the particular end-products desired to beobtained. In general, the vapor phase reactions are preferred becausethey can be carried out more economically, may be controlled more easilyand may be directed toward the production of the desired organosiliconhalides with a minimum of by-products.

Likewise, the invention is not limited to the specific temperatures ortemperature ranges mentioned in the examples. However, the reactiontemperature should not be so high as to cause an excessive deposition ofcarbon upon the unreacted silicon during the reaction. In general, thereaction temperature to be used will vary with, for example, theparticular hydrocarbon halide employed, the particular catalyst (if any)used and the yields of the specific reaction products desired to beobtained from a particular starting hydrocarbon halide. For example, byvarying the temperature of reaction within the temperature con halides'(e. g., phenyl silicon halides, etc.) the aryl-substituted aliphaticsilicon halides (e. 8., phenylethyl silicon halides, etc.) and thealiphatic-substituted aryl silicon halides (e. g., tolyl siliconhalides, etc.)

The products of this invention have utility as intermediates in thepreparation of other products. For instance, they may be employed asstarting materials for the manufacture of silicone resins. They also maybe used as agents for treating water-non-repellent bodies to make themwater-repellent as disclosed and claimed in the copending application ofWinton I. Patnode, Serial No. 365,983, filed November 16, 1940, andassigned to the same assignee as the present I invention. They also maybe employed for treatrange of, say, 200 to 500 C., the proportions ofthe individual products obtained when methyl chloride is brought intocontact with silicon can be varied and, also, the overall rate ofreaction of the methyl chloride. At temperatures of the order of 200 C.the reaction proceeds much more slowly than at reaction temperaturesaround 250 to 400 C. At temperatures much above 400 C.,

in the case of methyl chloride for example, there is a vigorousexothermic reaction which generally results in an undesirable depositionof carbon in the reaction tube. Although methyl silicon chlorides invarying yields can be produced by effecting reaction between methylchloride and silicon at various temperatures within the temperaturerange of 200 to 500 C., optimum results usually are obtained within themore limited range of iii) ing glass fibers in continuous filament orother form.

In copending application Serial No. 412,460 of Eugene G: Rochow andWinton I. Patnode, filed concurrently herewith and assigned to the sameassignee as the present invention, claims are made to a method ofpreparing hydrocarbonsubstituted silicon halides wherein is utilized asolid, porous contact mass of the kind briefly described under, forinstance, my above Example 7. As pointed out under that example, thesecontact masses and their preparation are more fully described andclaimed in copending Patnode application Serial No. 412,461, filedconcurrently herewith.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of preparing organosilicon halides which comprisesefiecting reaction between silicon and a hydrocarbon halide.

2. The method of preparing organosilicon halides which compriseseflecting reaction between silicon and a hydrocarbon halide in a vaporstate.

3. The method of preparin alkyl silicon chlorides which compriseseffecting reaction between silicon and an alkyl chloride.

4. The method of preparing aryl silicon'chlorides which compriseseffecting reaction between silicon and an aryl chloride.

5. The method .of preparing phenyl silicon chlorides which compriseseffecting reaction between silicon and chlorobenzene.

6. The method of preparing hydrocarbon-substituted silicon halides whichcomprises effecting reaction between silicon and the vapors of ahydrocarbon halide while the said components are intimately associatedwith a metallic catalyst for the reaction.

7. The method of preparing hydrocarbon-substituted silicon halides whichcomprises effecting reaction between silicon and the vapors of ahydrocarbon halide while the said components are intimately associatedwith copper.

8. The method of preparing hydrocarbon-substituted silicon halides whichcomprises effecting reaction between the vapors of a hydrocarbon halideand silicon in the form of an alloy thereof with a metal that is acatalyst for the reaction.

9. The method of preparing hydrocarbon-substituted silicon halides whichcomprises eifecting reaction between the vapors of a hydrocarbon halideand silicon in the form of an alloy thereof with copper.

10. The method of preparing methyl silicon chlorides which compriseseffecting reaction between silicon and methyl chloride.

11. The method of preparing methyl s'ilicon chlorides which comprisesefiecting reaction between silicon and methyl chloride while the saidform of an alloy thereof with copper.

15. The method of preparing methyl' silicon chlorides which comprisesbringing gaseous methyl chloride into contact with a mass of siliconintimately associated with copper, heating the said methyl chloride andsilicon-copper mass at a temperature sumciently high to eii'ect reactionbetween the methyl chloride and the silicon or the said mass, andrecovering the methyl silicon chlorides.

16. The method which comprises causing gaseous methyl chloride to reactwith silicon intimately associated with copper. said reaction beingcarried out within the temperature range of 200 to 500' 0., and coolingthe eiiluent cases to obtain a condensate comprising methyl siliconchlorides.

17. The method 01 preparing phenyl silicon chlorides which compriseseii'ecting reaction between silicon and chlorobenzene while the saidreactants are intimately associated with silver.

EUGENE G. ROCHOW.

